We have constructed a transposon-based vector system,pTNR.for creation of random large mutant library in various Rhodococcus species [1] This vector can create a single copy of insertion into Rhodococcus chromosomes with the advantage of easily identification of the insertion sile through the plasmid reseue from the genome pTNR was further modified to be used for protein expression [2].Currently four variants of pTNR vector are available,each with different antibiotic-resistance marker genes Nonetheless,single gene mutagenesis may be not suitable to characterize some phenotypes.